1) Field of the Invention
This invention relates generally to fabrication of a semiconductor device and more particularly to a method for laser marking a wafer without inducing flat edge particles.
2) Description of the Prior Art
Currently, semiconductor wafers are generally marked for identification and traceability. One approach to marking wafers is to cut a mark directly into the silicon layer of the wafer using laser scribing techniques. The mark is made by removing a volume of material from the silicon layer of the wafer. The removal of silicon material creates a silicon slag. As disclosed in an article by Chi-Shen Lo et al. titled "Integration Laser Marker for Flat Edge Particle Reduction", laser marking has been identified as the root cause of reduced yields from what is commonly referred to as flat edge particles. Analysis of the contaminating particles has shown them to be silicon removed by the marking process. A need exists for a method of laser marking semiconductor wafers without inducing flat edge particles.
The importance of overcoming the various deficiencies noted above is evidenced by the extensive technological development directed to the subject, as documented by the relevant patent and technical literature. The closest and apparently more relevant technical developments in the patent literature can be gleaned by considering the following patents.
U.S. Pat. No. 5,610,104 (Mitchell) shows a method for marking a mark on a silicon substrate. This patent teaches a method of laser marking a wafer by forming an insulating layer on the silicon surface, marking the insulating layer by laser scribing, then removing the silicon or oxidized silicon exposed by the laser scribing process using a wet etch process and removing the insulating layer.
U.S. Pat. No. 5,237,343 (Osada) shows a method for scribing ink jet heads.
U.S. Pat. No. 5,877,074 (Chang et al.) shows a method of laser marking a wafer.
U.S. Pat. No. 5,851,928 (Cripe et al.) discloses a method of isotropically etching a substrate.
U.S. Pat. No. 4,732,646 (Elsner et al.) recites a marking method comprising: forming holes in a masking layer, performing a high-energy ion implant, and etching into the substrate.
The article "Integration Laser Marker for Flat Edge Particle Reduction," (Chi-Shen Lo et al.) SEMI, IC Seminar (1997) identifies laser marking as the root cause of the flat edge particle yield reduction, and recites a method of reducing flat edge particle defects by controlling mark position and beam energy.